Piston structure and liquid feeder valve

ABSTRACT

Piston structure having a first side and a second side and in a recess ( 6 ) formed in an outer portion of the piston ( 1, 22 ) a resilient sealing element ( 5, 11, 21 ) is placed. The axial width and at least in some places the radial depth of the recess ( 6 ) are greater than the cross-sectional diameter of the sealing element ( 5, 11, 21 ) which is able to move, owing to the pressure difference of the two sides, between a first and a second position, thereby alternately ensuring a cumulated cross-sectional area at most A1, and a cross-sectional area A0, or a cumulated cross-sectional area at most A2, and a cross-sectional area A0. A1 and A2 are substantially smaller than A0. The invention further relates to a liquid feeder valve including this piston structure for allowing liquid flow-through in a certain amount or for a period of time from a pressurized source of liquid.

The invention relates to a piston structure for two-directional axialmotion in a piston cylinder containing liquid, the piston structure hasa first side facing a first chamber and a second side facing a secondchamber, a piston-rod is attached to the first or the second side of thepiston, and in a recess formed in an outer portion of the piston anO-ring made of a resilient material and having a given cross-sectionaldiameter is placed which seals the wall of the piston cylinder. Theinvention further relates to a liquid feeder valve for allowing liquidflow-through in a certain amount or for a period of time from apressurized source of liquid.

In liquid systems, for example in water-pipe systems there is often needfor enabling dosage of liquid in certain amounts or for a period oftime. There are valves which can be used for this purpose, for examplethe so called “Shell-valves”, such as water-closet flush valves. Thisapplication comprises a membrane and a relatively long and narrowconduit pipe with a cross-section of about 50 μm, which restricts thepressure of water and, by forming an auxiliary current, it blocks theflow path of the liquid after filling up a given volume. With use, theliquid flows through the thin passage in the same direction every time,and due to this, solid contaminants accidentally present in the liquidmay choke up the narrow passage. In such case the valve must bedisassembled and these contaminants can be removed from the conduit pipeby means of a thin wire pin which is after all a wearisome operation ofmaintenance.

U.S. Pat. No. 4,057,074 describes a valve design which is provided withan active piston displaceable in two directions. According to thisdescription the design is operable even in case of great pressuredifferences existing between the two sides, by means of a spring used inone of the spaces of liquid. However, this element may in itself be acause of failure.

The aim of the present invention is to provide a simple, reliable pistonand with this a feeder valve structure, which do not requiremaintenance, which are operable within wide-ranging limits, with whichliquid flow-through can be stabilized or can be changed in timeaccording to chosen characteristic and can be implemented at low cost.

It has been realised that:

when using a piston which comprises a resilient sealing element placedin a domain of its edge where the sealing element is able to assume twodifferent positions and move between them, different cross-section offlow can be provided, consequently different flow velocity can beobtained;

the two positions can be correspondent to two different directions offlow, thereby for example removal of possible contaminants can beperformed in a self-cleaning way.

To achieve the aim of the present invention, a piston structurementioned in the introductory part is provided, wherein the axial widthand at least in some places the radial depth of the recess formed in meouter portion of the piston are greater than the cross-sectionaldiameter of the O-ring, the O-ring is placed in the recess so that it isable to move, owing to the pressure difference between the first sideand the second side, between a first position facing the first side anda second position facing the second side, and when the O-ring is in itsfirst position the cumulated cross-sectional area of the flow pathbetween the recess and the first side of the piston is A1, and thecross-sectional area of the flow path between the recess and the secondside of the piston is A0, however, when the O-ring is in its secondposition the cumulated cross-sectional area of the flow path between therecess and the second side of the piston is A2, and the cross-sectionalarea of the flow path between the recess and the first side of thepiston is A0, where the smaller of A1 and A2 is smaller than A0 byorders of magnitude.

In another embodiment, where the liquid flow-through is stabilizedindependently of the pressure fluctuation, in the, piston structurementioned in the introductory part, the flow path having a cumulatedarea A1 is made up of one or more openings in the form of radialscraping, grooving, ribbing or engraving in one or more places on thebearing area for the sealing element of the piston, which openings arenarrowed down by the sealing element proportional to the pressuredifference when the higher pressure present in the second chamber thanin the first chamber deforms the sealing element elastically.

The invention will be described with reference to the attached drawingswhere:

FIGS. 1A and 1B schematically show the principle of the liquid feedervalve according to the invention with two different directions ofdisplacement;

FIGS. 2A and 2B show the cross-section of the liquid feeder valveaccording to the invention with two different directions ofdisplacement;

FIGS. 3A, 3B and 3C schematically show the cross-section of the sealingelement and the recess of the piston according to the invention indifferent positions and implementation, in which the sealing element isan O-ring;

FIGS. 4A and 4B show two possible shaping of the recesses which areformed in the sidewall of the piston cylinder according to the inventionfor programmed flow;

FIGS. 5A and 5B show in side elevation the piston of the liquid feedervalve of FIGS. 2A and 2B with two different directions of displacement,having a sealing element profiled differently in its cross-sectionalview; and

FIGS. 6A and 6B show the pressure equalizing flow-through regulatingfunction of the sealing element of the piston according to theinvention.

The piston structure shown in FIGS. 1A, 1B, 2A and 2B consists of apiston 1 movable in a piston cylinder 2 having circular cross-section, apiston shaft 4 mounted on piston 1, and an auxiliary piston 3 mounted onpiston shaft 4. The arrow shows the direction of flow of the liquid whenthe auxiliary piston 3 is in open position. The closed space bordered bypiston 1 forms a first chamber K1, while the space of liquid connectedto the liquid system and intercommunicating the second side of piston 1when auxiliary piston 3 is in open positions can be regarded as a secondchamber 12, which may be of different pressure than first chamber K1. Onan outer portion of piston 1, on its edge, a recess a is formed, whichin FIGS. 1A and 1B is shown schematically, representing only itsinterior shape. In recess 6 a sealing element which in the presentexample is an O-ring 5 having a circular cross-section and made of aconventional resilient material is placed, the diameter of which issmaller than the axial width and at least in some places smaller thanthe radial depth of the recess 6. As a result of this, the O-ring 5functioning as sealing is able to assume two different specificpositions as a function of the difference between pressure prevailing inthe first chamber K1 and second chamber K2 formed on the first side andsecond side of piston 1 respectively. In both positions, the pistonstructure is permeable to liquid to a certain extent. It is assumed thatin the first position of O-ring 5 the cumulated flow path between recess6 and first side of piston 1 (the side on the left in FIGS. 1 and 2) hasa cross-sectional area A1 determining liquid flow-through, and thecumulated flow-through between recess 6 and second side of piston 1 (theside on the right in FIGS. 1 and 2) has a cross-sectional area A2 in thesecond position. If hydraulic pressure is higher in second chamber K2,then O-ring 5 is in its first position, piston 1 moves in the directionof arrow M shown in FIG. 2A, and a gap having a cross-sectioncorresponding to area A1 determines liquid flow-through, that is therate of filling up of the first chamber K1, and through this the lengthof time until auxiliary piston 3 on piston shaft 4 closes free flow ofliquid along the arrow indicating the direction of flow. By moving ofpiston shaft 4 in the opposite direction, the conditions of pressuredifference between first chamber K1 and second chamber K2 will change,thereby in the second position of O-ring 5 (FIG. 2B), liquid being inthe first chamber K1 can flow into second chamber K2 through across-sectional area A2. Unmarked symbolic arrows of FIGS. 1B and 2B bytheir having greater thickness than arrows of FIGS. 1A and 2A indicatethe larger, more rapid liquid flow-through. On activating piston 1 isenforced by a certain mechanism to move towards the first chamber K1.This mechanism can be a valve to run down liquid from the first chamberK1 to a space of lower pressure through either the piston 1 or thepiston cylinder 2, or alternatively can be a direct mechanical mechanismfor moving the piston shaft 4 which may be performed manually or bymeans of any other servo structure coupled to piston shaft 4 asrequired. In the example according to FIG. 2 area A2 is essentiallylarger than area A1, thereby it can be assured that in case of freeliquid flow-through, the set timing well exceeds the time necessary forstarting the feeder valve, that is, the time necessary for pushingpiston shaft 4 up to a given point for example a point of “bump”.

Independent of whether O-ring 5 employed as sealing element takes up itsfirst or second position in recess 6 of piston 1, the measurement ofpiston 1 without sealing is such that cross-sectional cumulatedflow-through corresponding to a area A0 is possible between the pistonand the wall of the piston cylinder 2, and this cross-sectional area A0is substantially larger than A1 and A2, or at least larger than thesmaller of the two. In the present example A2 is larger than A1, and A0may approximately be of the order of A2, since it does not increase thelength of time being necessary for manual (mechanical) operation, foractivation of the piston structure.

FIGS. 3A-3C are enlarged drawings of the wall of piston cylinder 2, theedge part of piston 1 in which recess 6 is formed, and the sealingelement O-ring 5 placed in recess 6, In this preferred embodiment, thecross-sectional area A1 and A2 necessary for flow-through may beimplemented by forming grooves either in the wall of recess 6 or in thesurface of the O-ring 5. These grooves can be found both on the bottompart and side parts of recess 6 which has a rectangular cross-sectionalprofile. The dimensions (width and depth) of the grooves and also theirdenseness in the wall of the recess all together determinecross-sectional areas A1 and A2. The grooves can be formed by etching orthey can be scratched in using a hard tool, the latter is simplerconsidering the difficulties in access of the inner surface of therecess. Displacement of O-ring 5 between its first and second positionmay take place substantially without friction in the environment filledwith liquid, and, displacement is further promoted by allowance formeasure. In FIG. 3B where O-ring 5 is in its second position, it locksup, since it leans against the flat wall of recess 6 which wall is atthe second side (the right side in the Figure). In this case A2=0. Inthe case of FIG. 30 A1 is larger than A2, but, the latter is also largerthan 0.

Flow operation of the feeder valve having a principal piston and anauxiliary piston shown in FIG. 2, that is, setting the characteristicsof operation of the feeder valve in terms of time, can be done bychoosing the cumulated measurements of the openings for flow-through(A1, A2, as well as by adjusting the opening point of auxiliary piston3. It is easy to see that displacement of piston 1 means travelling ofthe sealing element along the inner wall of piston cylinder 2. Thismakes possible formation of the respective areas (A1 or A2) of openingsfor flow-through between the sealing element and the wall of the pistoncylinder 2 instead of forming them between the sealing element and thewall of the recess 6. in this way ensuring flow-through in compliancewith the instantaneous location of, displacement and thereby variablespeed of piston 1. This may be needed for example when auxiliary piston3 is moved in the vicinity of its closing or opening point, whensignificant braking effect is needed for damping—as much as possible—the“shock” occurring for example at the time of closing. It can be veryimportant in case of liquid feeder valves used in industry, whererespectable quantities of flow-through are needed and mechanical stressof the system would be greater without braking. This kind ofaccomplishment, that is, when area A1 is variable depending on theposition of piston 1, may be assured by recesses 7, 8, as it is shown inFIG. 4. FIG. 4A illustrates recess 7 which provides a linearlydecreasing cross-section, and FIG. 4B shows recess 8 by means of whichthe cross-section can be altered linearly as well as steplike(immediately), thereby realizing a peculiar characteristic of velocityin time.

In FIGS. 5A and 5B two positions of sealing element 11 of piston 10 areshown respectively, illustrating the direction of liquid-flow and thedirection of displacement M of the piston. This example shows that it isnot necessary for sealing element 11 to be formed as O-ring, but othersealing having an annular cross-section can be used, which is suitablefor assuring the required sealing by leaning against the wall of therecess and the wall of the piston cylinder. The arrows indicating theflow-through are shown at the line of the axis, in relation to this itshould be noted that in the condition which makes more rapidflow-through possible, that is when area A2 is larger, the opening forflow-through between the second side of piston 10 and the recess may bealso realized on other parts of the piston, for example by formingboreholes in the piston-body. These boreholes may connect the internalspace of the recess and the second side of piston 10. The piston 10illustrated in side elevation in FIG. 5A and FIG. 5B includes a radial Ushaped groove 12, with a difference that the right side of the piston 10is cut through along one leg of the U shape being transversal to theplane of drawing.

In the spirit of the present invention, built upon a common ground,there are further possibilities for constructing a piston structure inwhich the sealing element through its elastic deformation narrows downthe opening for flow-through having a area A1 proportionately to themeasure of pressure difference between the first side and the secondside. The operation of this is shown in FIG. 6, where FIG. 6Aillustrates the position of sealing element 21 which is by way ofexample realized as an O-ring. The sealing element 21 lies above opening23 formed on an inner surface (looking onto the first side) of therecess of piston 22. This is the situation when pressures on the firstside and on the second side substantially equal to each other or thereis only a slight difference between them. However, in case of liquidsystems with high pressure, it may occur that this difference is great.Then flow of liquid through opening 23 would be more rapid, which can becompensated by elastic deformation of the sealing element as shown inFIG. 6B, where a portion of the O-ring deflects thereby it narrows downthe effective cross-section of opening 23. In this manner, byappropriate choosing of the size of opening 23 as well as the materialof the sealing element 21, the narrowing down of the cross-section(performed in the interest of uniformity of flow-through measured duringa unit of time) is directly proportional to the invert of flow velocity.This self-adjusting structure can be used also in case of valves wherethe piston does not perform reciprocating motion. Still, all these canresult in useful side effects in case of liquid feeder valves performingtwo-directional motion, too.

In the liquid feeder valve structures like in FIGS. 1 and 2 it may be aproblem to open the auxiliary piston 3 from its fully closed state. Incase of high liquid pressure and large sizes the force caused by thepressure on the auxiliary piston 3 disables to open it with the pistonshaft 4. It may be a considerable problem, especially in case of handoperated mode, but in case of applied servo machine reduction of thepower need is also desirable. For this purpose the high pressure liquidcan be run down from the closed space of first chamber K1 withoutdisplacing closed auxiliary piston 3. It can be achieved in differentmanners, all having the common feature that the high pressure liquidfrom first chamber K1 is getting to a space of lower pressure througheither the piston 1 or the piston cylinder 2. In this case the area A2is not relevant, it may be zero.

In the arrangement of FIG. 7A a further control valve 1′ is formedwithin the piston 1, which enables the liquid to flow from first chamberK1 to a low pressure space K3, which is a liquid outlet indeed. Controlvalve 1′ can be opened by another piston shaft 4′ which passes throughthe hollow body of piston shaft 4″ connecting piston 1 to auxiliarypiston 3. The piston shaft 4′ can move independently from piston shaft4″. The control valve 1′ of small area can be opened against tiny force,and after release pressure and run down liquid from the first chamberK1; the high pressure liquid in second chamber K2 will have the piston 1moved toward the first chamber K1 during the opened period of controlvalve 1′, and the main liquid stream flows into the space K3 asillustrated in FIG. 78. A spring S is used to return control valve 1′into its closed state when the piston shaft 4′ is released. Then thepiston 1 together with auxiliary piston 3 will move in reverse directionat a speed dependent on area A1 until auxiliary piston 3 closes the mainstream.

In the arrangement of FIG. 8A a controllable valve V in the wall ofpiston cylinder 2 is used to release pressure and run down liquid fromthe first chamber K1. Opening and closing valve V provides a controlcorresponding to that of the control valve 1′ described above, asillustrated also in FIG. 5B. The piston shaft 4 is different from thesimilar element of FIGS. 1 and 2 in that initiating and timing the mainstream flow period is activated by valve V instead piston shaft 4 ofFIG. 8, which requires a small power also in this case. The foregoingstructures fundamentally concern liquids. However, It should be notedthat by forming micro-sized radial scraping, grooving, ribbing orengraving on the bearing areas in one or more places, the components areable to perform the aforementioned asymmetrical operation in case ofgases, for example in case of gaseous shock absorbers or dampers. Thusthe invention can be used in connection with any fluid, either liquid orgaseous fluids.

A significant advantage of the present invention is that when it is usedas valve, then two-directional operation results in self-cleaning, andthere is no need for using complicated tools. For putting into practice,asymmetry (A1<<A2) is essential in terms of proportioning activation andrequired time of operation. Finally, on the one hand, the technique usedmakes it possible to realize a characteristic of flow-through whichchanges in time, on the other hand, it makes possible to keep thischaracteristic steady irrespective of the pressure fluctuation of thesource.

1. Piston structure for two-directional axial motion in a pistoncylinder containing liquid or gaseous fluid, said piston structure has afirst side facing a first chamber (K1) and a second side facing a secondchamber (K2), a piston shaft (4) is attached to said first or secondside of said piston (1), and in a recess formed in an outer portion ofsaid piston (1) an O-ring (5) made of a resilient material and having agiven cross-sectional diameter is placed which seals the wall of saidpiston cylinder (2), the axial width and at least in some places theradial depth of said recess (6) formed in the outer portion of saidpiston (1) are greater than the cross-sectional diameter of said O-ring(5), the O-ring (5) is placed in said recess (6) so that it is able tomove owing to the pressure difference existing between the first sideand the second side, between a first position facing the first side anda second position facing the second side, characterized in that, whensaid O-ring (5) is in its first position the cumulated cross-sectionalarea of a flow path between said recess (6) and the first side of saidpiston (1) is A1, and the cross-sectional area of a flow path betweensaid recess (6) and the second side of said piston (1) is A0, and whensaid O-ring (5) is in its second position the cumulated cross-sectionalarea of said flow path between said recess (6) and the second side ofsaid piston (1) is A2, and the cross-sectional area of said flow pathbetween said recess (6) and the first side of said piston (1) is A0,where the smaller of A1 and A2 is smaller than A0 by orders ofmagnitude, and in the first and second position the direction of thepossible liquid flow between first and second chambers (K1,K2) isopposite.
 2. Piston structure according to claim 1 characterized in thatA1 and A2 are different.
 3. Piston structure according to claim 1,characterized in that said flow path in said recess (6) is realized byforming radial scraping, grooving, ribbing or engraving in one or moreplaces on the bearing area of said O-ring (5).
 4. Piston structureaccording to claim 1, characterized in that said flow path is realizedby forming radial scraping, grooving, ribbing or engraving in one ormore places of the bearing area of said O-ring itself.
 5. Pistonstructure according to claim 1, characterized in that said O-ring (5)owing to the pressure difference existing between the first side and thesecond side, is able to become deformed and to bend into said flow path,thereby it is able to reduce the cumulated cross-sectional area A1 or A2of said flow path proportional to the pressure difference.
 6. Liquidfeeder valve for allowing liquid flow-through in a certain amount or fora period of time from a pressurized source of liquid, characterized inthat said feeder valve comprises the piston structure of claim 1,wherein said piston shaft (4,4″) operates an auxiliary piston (3)installed in the main stream flow path of the liquid, said piston (1) isset in motion towards said first chamber (K1) by a driving mechanism,and said second chamber (K2) is coupled to a lower pressure space (K3)in the open state of said auxiliary piston (3).
 7. Liquid feeder valveaccording to claim 6 characterized in that A2 is larger than A1 byorders of magnitude.
 8. Liquid feeder valve according to claim 1,characterized in that, at least one of said areas A1 and A2 is chosen tobe of such a size that braked closing of said piston (1) is assured. 9.Liquid feeder valve according to claim 8, characterized in that whensaid piston (1) moves in two directions, the degree of braking of saidpiston (1) at the time of closing is different.
 10. Liquid feeder valveaccording to claim 6, characterized in that said driving mechanism is apush-button mechanism whose travel-path is limited to a given length.11. Liquid feeder valve according to claim 6, characterized in that saiddriving mechanism is a push-button mechanism whose travel-path can belimited to several given lengths.
 12. Liquid feeder valve according toclaim 10, characterized in that limitation of said travel-path of thepush-button is adjustable by means of a limiting mechanism variable byturning along a helical path.
 13. Liquid feeder valve according to claim12 characterized in that it is at least provided with a push-buttontravel-path of which is adjustable by turning and with a push-buttontravel-path of which is limited to a fixed length.
 14. Water-closetflush valve characterized in that it comprises a liquid feeder valveaccording to claim
 1. 15. Liquid feeder valve for use in chemicalindustry characterized in that it comprises a liquid feeder valveaccording to claim
 1. 16. Timing valve for sprinklers used in gardenscharacterized in that it comprises a liquid feeder valve according toclaim
 1. 17. Piston structure for two-directional axial motion in apiston cylinder containing liquid or gaseous fluid, the piston structurecomprises a piston (22) in an outer portion of which a recess is formedin which a sealing element (21) made of a resilient material and havinga given cross-sectional diameter is placed which seals the wall of saidpiston cylinder, said piston (22) has a first side facing a firstchamber (K1) and a second side facing a second chamber (K2), a cumulatedcross-sectional area of a flow path between said recess and said firstside of said piston is A1, said recess is coupled to said second chamber(K2), characterized in that said flow path having a cumulated area A1 ismade up of one or more openings (23) in the form of radial scraping,grooving, ribbing or engraving in one or more places on the bearing areafor said sealing element (21) of said piston (22), and said openings(23) are narrowed down by said sealing element (21) proportional to thepressure difference when the higher pressure present in said secondchamber (K2) than in said first chamber (K1) deforms the sealing element(21) elastically, and in the first and second position the direction ofthe possible liquid flow between first and second chambers (K1, K2) isopposite.
 18. Liquid feeder valve according to claim 17 characterized inthat said sealing element (21) is an O-ring.
 19. Liquid feeder valveaccording to claim 6 characterized in that the cross-section of saidpiston cylinder (2) and said piston (1) engaged within is oval. 20.Liquid feeder valve according to claim 6 characterized in that area A1is variable depending on the position of said piston (1) and is ensuredby means of recess (7, 8) formed in the wall of said piston cylinder(2).